The present invention concerns amine-treated thio-bis-(alkyl lactone acid) and thio-bis-(hydrocarbyl diacid) materials, their metal complexes, their method of preparation and their utility, preferably, in hydrocarbon fuel and lubricating systems, as stable sludge dispersants, varnish inhibitors, lubricity agents, and antioxidants.
During the past decade, ashless sludge dispersants have become increasingly important, primarily in improving the performance of lubricants and gasoline, in keeping the engine clean of deposits, and permitting extended crankcase oil drain periods. One category of ashless dispersants concerns acylated nitrogen-containing compounds which can be prepared via the acylation of polyalkylene polyamines, e.g., tetraethylenepentamine, with such acylating reagents as: (i) polyalkenyl succinic anhydrides as taught in U.S. Pat. Nos. 3,172,892, 3,219,666, and 3,272,746; (ii) chlorinated alkenyl succinic acid derivatives as taught in U.S. Pat. No. 3,996,240; (iii) halolactone acid derivatives as featured in U.S. Pat. No. 3,620,977; and (iv) simple lactone acids as taught in U.S. Pat. Nos. 3,200,075, 3,261,782, 3,487,452, 3,734,865, 3,936,472, 4,132,531 and British Pat. No. 1,420,962. However, dispersants of this category are susceptible to oxidative degradation especially under high severity conditions engendered by elevated oil temperatures and extended drain intervals. Such dispersants tend to break down and promote sludge and deposit formation. Besides instability problems, the inherent limitations in sludge binding properties of this class of dispersants tend to diminish their potency as the severity of operating conditions increases.
In the prior art, several attempts were made to stabilize dispersants of category (i) by incorporating, for example, sulfur into the molecule as taught in U.S. Pat. Nos. 3,309,316, 3,390,086 and 3,470,098. Because of the nature of the synthetic pathways selected in these prior studies, however, the sulfur that was incorparated into such dispersants was unstably bonded and as a consequence, tended to promote sludge and varnish formation.
The present invention by virtue of new synthetic approaches, overcomes the shortcomings of the prior art by designing novel, aminated thio-bis-(polyalkyl lactone acid) and thio-bis-(hydrocarbyl diacid) materials with enhanced stability and potency. The stabilization of these novel dispersant systems may be related to the introduction of stable mono- and disulfide functionality which imparts to these systems enhanced antioxidant properties. The enhanced potency may be ascribable to the macrocyclic and/or macrocyclic-like configurations assumed by the polar sullfur and nitrogen (heteroatom) functionality in some of the dispersant molecules. Such circular-like arrangements of ligands endow these novel systems with remarkable binding and/or chelation properties and in some instances, inclusion properties, making these dispersant systems uniquely effective even under high severity conditions.
It is a further object of this invention to provide novel and improved dispersant systems based on host guest chemistry wherein the polar head of the host molecule (dispersant) assumes or is capable of assuming a macrocyclic-like configuration so that the resulting circular-like array of heteroatoms (e.g. sulfur, oxygen and nitrogen), on the polar head effectively binds guest ions and molecules, including metals and sludge components, within the cyclic-like structure, or between host molecules to form a sandwich-like structure with guest molecules in the middle.